The light emitting device, such as a light emitting diode of III-V group or II-VI group compound semiconductor or a laser diode, can produce various colors, such as red, blue, and ultra-violet owing to development of the thin film growth technology and device materials therefor, as well as a white color of good efficiency by using a fluorescent material or mixing colors, and is advantageous in that the light emitting device has power consumption lower than the present light sources, such as a fluorescent light and an incandescent light, a semi-permanent lifetime, fast response speed, and safety, and is environment friendly.
Accordingly, application of the light emitting device is expanding even to transmission modules of optical communication means, a light emitting diode back light unit which is replacing the CCFL (Cold Cathode Fluorescence Lamp) back light unit in an LCD (Liquid Crystal Display) device, white light emitting diode lighting devices which are replacing a fluorescent light and an incandescent light, car head lights, and signal lamps.
In the meantime, though the light emitting device may be fabricated to include a nitride semiconductor layer formed on a substrate, a lattice mismatch between the substrate and the nitride semiconductor is liable to cause a lattice defect.